Judge of Stroke (JOS)

The primary role of the JOS is to ensure that every swimmer has a fair and equitable opportunity to perform and that the swimming is in accordance with the rules related to the designated stroke or event. The JOS must know the rules and how to apply them. The rules must be applied to the swimming stroke being swum with uniformity whether it is a club, regional or national level competition. 

Observation of the Swimmers to verify conformity with the Rules,

Although the outside lanes are the easiest to see, all assigned lanes must be watched equally. The JOS's attention must be on the swimmers at all times. The shift of eyes from head, to arms, to feet and from lane to lane, will vary. Positioning is the key to a good performance as a JOS.

Rule Infringements

The stroke rule is either broken or it is not - there is no middle ground.  When working as a JOS, if you observe a rule infraction, advise the other JOS and head to see the referee as quickly as possible. Discuss the infraction with the referee and complete the DQ form if asked to do so. The Referee will most likely be alerted to your pending DQ by the fact that you are out of position on poolside. The disqualification form must include the event, heat, lane number and a written description of the infringement. The wording must be in accordance with the rules. (See the SNZ Technical Advisory Committee’s ‘Swimming Rule Quick Reference Infraction Card’ as a guide). It must also be signed by the JOS recommending the disqualification. If a protest is lodged against the disqualification you may be required to report what you saw to the Jury of Appeal.

Pool side position for JOS

For New Zealand Championships and Competitions, four JOS's shall be appointed. The Technical Director will allocate each JOS to their positions. The Referee will advise you of any special rules that might apply to the meet and any other responsibilities that he/she may require the JOS to undertake during the meet.

The JOS assignment begins after the start of the race. At the start JOS' stand in a position to ensure the swimmers comply with the rules of start for the stroke being swum. This is approx 5m to 7m from the start end for backstroke, breaststroke, butterfly and individual medley and 10-15m for freestyle.  In freestyle, backstroke and butterfly JOS' need to be aware of the 15m mark and ensure some part of the swimmers’ head has broken the surface of the water prior to or at the 15m mark.

Watch the swimmers approaching you and ensure they are complying with the rules for the designated stroke. JOS's will also be required to drop the false start rope if a false start is signalled by the Referee or Starter. Prior to the session starting ensure you have checked how the false start rope mechanism works and that it is in operational order.

At the start of breaststroke races, JOS' are in position to observe the swimmers head breaking the surface of the water before the hands turn inwards at the widest part of the second stroke. This is at approx 10 to 14m from the start end. It will vary depending on the age and gender of the swimmers. The above responsibilities are reversed for turns or starts (long course 50m events) at the turn end of the pool. For turns at the start end the procedure is the same as during the start.

After the start the JOS follow behind the feet of the last swimmer observing that the rules of stroke for the designated stroke are complied with. When the swimmers spread out, the lead JOS remains behind the feet of the lead swimmer/s, while the trailing JOS remains behind the feet of the last swimmer. When the swimmers turn your roles will reverse.

In events e.g. 400m individual medley, where there is likely to be a big spread of swimmers, it is necessary to be aware of where your fellow JOS is positioned. If he/she is caught up at the turn with swimmers still to complete the turn it may not be possible for them to be able to observe the 15m mark for the swimmers coming off the wall at the other end of the pool. If this occurs, it is important that you position yourself to be able to cover this for your colleague. It is most likely he/she will have to cover for you at the next turn. As JOS it may be necessary to fill in for the Referee if he/she is called away for any reason. Don’t forget to have your whistle with you.


When working as a JOS you will need to have with you a whistle, pen and a copy of the FINA rules. These items plus any others you have should be positioned on poolside near you so that you can get them when you require them. Do not carry these items with you during the race. Your dress should be of a high standard as your role is a very visible one.